Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a structure.
Description of the Related Art
A 3D modeling method for creating an arbitrary 3D object by laminating paper or film processed into a cross-sectional pattern of the 3D object has been proposed. This method is called a sheet laminating method, in which a 3D object is obtained by cutting previously prepared sheets using cutter or laser, and laminating the sheets. Therefore, the foregoing method is advantageous in thickness accuracy of layers and an apparatus to implement the method may be assembled with a relatively simple configuration as compared with other laminating 3D modeling methods.
As an exemplary method for modeling such a 3D object, a lamination modeling method in which a material which is to be modeled as a 3D object is laminated and creates a final structure has been proposed.
A restriction characteristic to the lamination modeling method is the need of a support. In the lamination modeling method, layered-shaped patterns are laminated. Therefore, for example, a modeled product in which an isolated portion (i.e., an overhung portion), such as a drooping branch of tree, is created during the manufacturing process is difficult to manufacture. In order to create such a portion by lamination molding, it is necessary to build a “support” at a lower portion which may become the isolated portion. The support is unnecessary in the final product state and should be removed the support by a certain means after the end of the modeling.
Also in the sheet laminating method, a support is necessary in modeling an overhung portion. Basically, the support is formed in the following manner: the sheets are laminated without removing cut margins and, removing the margins after the modeling is completed to create the support.
However, since the sheet is a single solid material, if the target object has a complicated shape, it is difficult to remove margins after modeling is completed. Therefore, it has been extremely difficult to create a highly accurate modeled product by the sheet laminating method.
In contrast, there is a method to form a support by different material from that of the modeling material in order to reduce removal of the support.
In this method, the support may be removed easily by using a solubilizer which makes the support member dissolve and not make the molding material dissolve. Further, if a material which is easy to remove although does not dissolve is used, workload may be reduced significantly.
U.S. Patent No. 2001/0042598 discloses the following method. After forming a layer of a 3D object (a model portion) by a modeling material in an apparatus, a material which becomes a support is provided to surround the layer, and patterning is performed. A support member (a support) is formed in this manner and, on the support and the layer of the 3D object under formation, a material which becomes the 3D object is laminated. According to the disclosed method, since the support portion is made of a material different from that of the model portion, removal of the support is also easily performed.
In the method disclosed in U.S. Patent No. 2001/0042598, however, it is considered that the thickness accuracy of the layers is not enough. In the lamination modeling method, sufficient accuracy is needed also for the thickness of the layers to be laminated in order to implement accurate modeling. If the 3D object to be modeled and the support are made of different materials as in the method disclosed in U.S. Patent No. 2001/0042598, the following problems may be caused. The first problem relates to the alignment between the 3D object to be modeled and the support portion. If these portions are misaligned, a gap is formed and, therefore, an overhung portion is not able to be supported. If the modeling material and the support portion overlap each other, there is a possibility that a protrusion is formed, or adhesiveness on a surface of the modeling material is reduced. As a result, strength of the 3D object may be reduced. The second problem relates to volumetric shrinkage. Forming layers of uniform thickness by different materials requires difficult control from the viewpoint of accuracy at the time of supplying the materials and volume change influenced by the environment. As described above, in the method disclosed in U.S. Patent No. 2001/0042598, there is a problem that an accurate alignment mechanism is needed and that thickness accuracy of the layer to be laminated is not enough.